


Brush And Floss

by gaymumbling



Category: A.C.E (Beat Interactive Band)
Genre: Anal Sex, Cockwarming, Established Relationship, M/M, Monsterfucking, Oral Sex, Tooth Brushing, monster byeongkwan
Language: English
Status: Completed
Published: 2021-03-18
Updated: 2021-03-18
Packaged: 2021-03-27 11:20:20
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,921
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/30121962
Author URL: https://archiveofourown.org/users/gaymumbling/pseuds/gaymumbling
Summary: “The flossing’s done, then?” Yuchan asked, placing the second used piece of floss on the table alongside the first. The fingers of his unoccupied hand flitted over the hem of Byeongkwan’s t-shirt.“I would say so, yeah,” Byeongkwan chuckled. “Go ahead, take it off.”Or, Yuchan notices a bit of food stuck in his monster boyfriend's teeth and gets an idea.
Relationships: Kang Yuchan | Chan/Kim Byeongkwan
Comments: 4
Kudos: 16





	Brush And Floss

**Author's Note:**

> i got this idea one night when i'm pretty sure dae's brain possessed my body for a very sexy 5 minutes, so blame them for... this <3 i hope you all enjoy my first a.c.e fic!! :D

When they moved into their new apartment together, Yuchan insisted on taking the left side of their king sized bed. Byeongkwan was confused, because at their last place he’d commandeered the right side, but knew better than to expect a sensical answer if he asked about it so he just resigned to never knowing the reason. If he had asked, however, there would’ve been a simple answer: the left side of the bed allowed Yuchan to lay with his back toward the window where the moon rose every night, and he loved the way its light danced across Byeongkwan’s slightly iridescent skin and shone on his teeth when he cracked a sleepy smile.

Those were the very same teeth that practically made Yuchan jump out of his skin the first time he saw them. The pair had been dating for a handful of months, and one evening Yuchan had gotten lonely while Byeongkwan was taking a shower. The rushing water drowned out the sound of Yuchan tapping on the door, so he took the initiative and entered the room anyway—a decision for which he apologized profusely upon realizing that Byeongkwan had wanted to be alone for a reason.

For his part, Byeongkwan apologized as well for hiding this less-than-human side of himself from his boyfriend, but all was well after Yuchan cooked dinner and they spent an evening cuddling on the couch while gently discussing the logistics of Byeongkwan’s other form. It was a side of him that Yuchan quickly grew to love, as Byeongkwan grew more and more relaxed about shedding his human disguise around the house. He once let it slip that it was more comfortable for him to breathe without the restrictions of human skin, whatever that meant; Yuchan honestly didn’t want to know, but he insisted that Byeongkwan shift forms when they were alone in the apartment or around guests if he was comfortable enough with them.

Yuchan could look at his monster boyfriend’s true form in all his glory whenever he wanted. Byeongkwan could... breathe better, apparently. It was a win-win situation.

***

“Smile for me.”

Byeongkwan looked up from his laptop to meet Yuchan’s gaze where he was sitting on their brand new couch in their brand new living room. 

“You’ve been staring daggers through your computer screen for hours,” Yuchan elaborated, getting up to walk over to his boyfriend. He gently picked up the computer and set it on the coffee table, then situated himself so he was kneeling with one thigh on either side of Byeongkwan’s lap. “So come on, let me see those teeth. Or even just a grin. It makes me sad to see you stressed.”

Yuchan pouted for emphasis.

Byeongkwan settled on giving him a grin.

“See? There you go, you big baby. Relax those cheek muscles!” Yuchan began rubbing circles on Byeongkwan’s cheeks as he was finding it more and more difficult to suppress a smile. “You know- it takes 17 muscles to smile and-”

“And 43 to frown, I know.” Byeongkwan couldn’t hold it in anymore, and let his smile grow. After a few moments he let it grow even larger than he knew a human smile should be, just to hear Yuchan shriek and wiggle in his lap.

“That’s not what I meant and you know it,” Yuchan said, but was given away by the squishy smile of his own and his hearty laugh sounding throughout the apartment. He moved his hands down away from Byeongkwan’s cheeks and around the back of his neck, and leaned down to place a little kiss on his forehead.

“Love you~” Byeongkwan said, as a blush the color of the northern lights rose and danced across his cheeks.

“Love you too baby, but you’ve got something in your teeth. Looks like a bit of meat.” Byeongkwan used his tongue to search around for the offending bit of food and hummed when he felt it. “At least I know you ate today, hmm?”

“Mmm, what are you going to do with me, right?” Byeongkwan teased, as Yuchan got up from his lap. “Could you grab some floss for me?”

“I really have to do everything around here, huh,” he called back. “Hey! I can hear you getting up- sit back down, relax, I’m already halfway to the bathroom...”

His voice trailed off as he got farther away. Soon enough, Byeongkwan could hear the bathroom cabinet door sliding open while Yuchan retrieved the floss.

“What, do you want me to be your little dentist too?” Yuchan joked when he was back in earshot.

And oh—that’s not an offer he was expecting to hear Yuchan make, even as a joke. Byeongkwan’s teeth were large and sharp. His boyfriend knew this; it was part of the reason he figured it wasn’t a completely serious offer. But...

“Well, if you’re offering,” Byeongkwan said, patting the spot on his lap Yuchan had occupied moments earlier, “I won’t say no to the help.”

Byeongkwan hoped his raised eyebrow was enough to signal to Yuchan that he was asking his own question as much as he was answering Yuchan’s.

“I...” Yuchan trailed off as he stepped closer to the couch. Now it was his turn to blush, his peachy pink a contrast to Byeongkwan’s returning greens and blues. Byeongkwan watched as Yuchan ran about a hundred anxious calculations in his head before finally settling back down across his lap. “Yeah, I’ll help.”

The two fell into a somewhat weighted silence, broken only by a plastic pop as Yuchan opened the lid of the floss, followed by a quiet whir while he pulled out a suitable length. He wound it around his two index fingers, and holy shit, this was happening.

“Open wide,” Yuchan said, cheerful to mask the slight anxiety brought on by trying something new, but still reverent in the way he regarded every aspect of Byeongkwan’s less-than-human form. His lips parted and he opened his mouth, showing the full extent of his large, razor-sharp teeth. He kept his long pointed tongue tucked back though, so it wouldn’t get in the way.

Yuchan shifted in his lap to get a better look and to get to work on the task at hand. Byeongkwan’s breath hitched in his throat at even such a small movement, the sound only adding to the heat already pooling in the pit of Yuchan’s stomach. He leaned in close to inspect Byeongkwan’s open and waiting mouth.

“Is this going to affect you the same way it’s affecting me?” Byeongkwan asked, careful not to move his lips too much lest he interrupt Yuchan’s view.

Yuchan bit his lip and laughed coyly in response. “Hmmm, you tell me,” he said, purposefully but only barely grinding his hips this time.

A staccato whine made its way up Yuchan’s throat while Byeongkwan shivered, and they each had their answer.

“Hold still, baby,” Yuchan said, lifting his hands to finally bring the floss up to Byeongkwan’s waiting mouth. “I know we technically had an actual goal here, but I’m just going to go ahead and floss between all of them, hmm?”

Byeongkwan nodded. He had absolutely no objections to Yuchan drawing this out as long as he damn well pleased.

So Yuchan got to work, easing the piece of floss between two of the teeth in the back of Byeongkwan’s mouth, pulling it out, and adjusting the floss between his fingers, repeating along the line of deceptively beautiful teeth. He knew if he slipped they would instantly pierce his skin, which in all honesty made this all the more exciting. When he made it to the end of his first piece of floss, he leaned over the arm of the couch to place it on the table. He winced leaving it out like this, but figured it could be thrown away properly later; he had much more important matters to attend to.

Yuchan pulled out another piece of floss, now finally getting to the original offending piece of food caught between Byeongkwan’s teeth. He gently worked it out, then moved on to the next teeth. He was working hard to concentrate despite the hardness he could feel growing between each of their legs, and made the mistake of flicking his eyes up to meet Byeongkwan’s watching him with as much intensity as he was focusing on the task at hand. The heated stare caused Yuchan’s hands to falter, and his fingers were met with the deadly points of a couple of Byeongkwan’s teeth.

He hissed and let go of the floss with his now injured hand, pulling it close to his face to inspect the cuts. He didn’t get too far, however, before Byeongkwan grasped his hand in his own to look at it for himself.

“Oh, that’s kinda deep, I’m sorry,” he said, as beads of blood began to bloom from the cuts. “Let me clean them off for you.”

Yuchan was given no time to protest before Byeongkwan was putting his fingers in his mouth and curling his tongue around and between them. Yuchan gasped as Byeongkwan sucked gently, then swallowed thickly around his fingers. He let go of Yuchan’s wrist but licked tenderly at his fingers as he removed them from his mouth. Yuchan ran his spit-slick fingers over Byeongkwan’s plush lips before trailing them across his cheek and down his neck, leaving a trail of goosebumps in their wake.

“The flossing’s done, then?” Yuchan asked, placing the second used piece on the table alongside the first. The fingers of his unoccupied hand flitted over the hem of Byeongkwan’s t-shirt.

“I would say so, yeah,” Byeongkwan chuckled. “Go ahead, take it off.”

Yuchan wasted no time slipping his hands under the hem of his shirt and pushing it slowly up his torso. Byeongkwan lifted his arms to make it easier to remove, and Yuchan placed it next to them on the couch. They met each other halfway in a soft kiss as Byeongkwan’s hands rested on the tops of Yuchan’s thighs. The kiss quickly became more heated. One of Yuchan’s hands found the junction of Byeongkwan’s neck and shoulder before travelling up to tangle in his hair, while the fingers on his other dug into the hard muscle of his pectoral.

Byeongkwan quickly shifted his teeth to be less deadly lest he caused Yuchan to bleed even more that afternoon, and pressed his tongue to the center of his lips to coax them open. Yuchan made a happy noise in the back of his throat while Byeongkwan’s tongue slipped between his lips and he gripped his thighs tighter. They kissed just like that for a few moments, finding an easy rhythm against each other’s mouths, until Yuchan got impatient and moved to kiss and lick down Byeongkwan’s throat. He left a couple marks on his neck and collarbones that would likely fade by the morning while he fumbled blindly with the buckle on Byeongkwan’s belt.

He laughed lightly at Yuchan’s struggle, and Yuchan joined in when he pulled back to get a better look at the buckle in question. Yuchan got it and his pants undone, then knelt on the floor while Byeongkwan spread his legs and shimmied his pants off.

“I have an idea, if you’re interested,” Yuchan said while Byeongkwan placed the pants with his shirt on the couch.

“Hmm? Whatcha got?”

“You know, I think it’s a little silly to floss without brushing, right?” Yuchan started, avoiding eye contact by drawing swirling patterns across Byeongkwan’s thigh. “And I obviously want to suck your dick. There’s no mystery there.”

“Uh huh...?”

“So like, what if I sucked you off, but then sat on your cock while I brushed your teeth?” He rushed through the question, only looking up at Byeongkwan’s face after the last word made it out.

Byeongkwan’s blush made it well past his cheeks, now covering his neck and even the top of his chest. He licked his lips, then rolled them together while he processed Yuchan’s request.

“I absolutely could not agree more. Let’s do it,” he said, reaching out a hand to bury it in Yuchan’s hair. “Are you stretched?”

“Always,” Yuchan said, and Byeongkwan guided his head down to hover over his waiting cock.

He placed a cheeky kiss on the tip before taking it slowly into his mouth, wrapping his hand loosely around the base. At the first contact, Byeongkwan’s grip tightened in his hair, and Yuchan could feel the tips of his claws digging into the base of his neck. He sunk down further until the head of Byeongkwan’s cock brushed the back of his throat, then pulled back to repeat the motion and set a slow and steady pace. Yuchan was no stranger to deepthroating his boyfriend’s dick, there was only so much space in his mouth and he was dating a monster, after all, but this was only the introduction to the afternoon’s more explicit activities. Yuchan didn’t want to get ahead of himself.

As he kept up the pace, making sure to give just as much attention to the base with his hand, he could hear Byeongkwan’s breath beginning to falter above him. The grip in his hair became more desperate. When Yuchan looked up to meet Byeongkwan’s gaze, he saw the stern look of a disheveled monster trying to keep his cool. His jaw was tight and his eyebrows were furrowed, and his breath was coming out of his nose in staccato puffs, the scalding heat of which Yuchan could feel on his face even from so far away. As their eyes met, Byeongkwan’s pupils were barely visible, each a pitch black line no thicker than a piece of paper; the molten gold of his irises bored into Yuchan’s deep brown ones and sent a shiver down his spine.

Yuchan groaned around Byeongkwan’s cock, and Byeongkwan could barely stop himself from thrusting up into his mouth. With his free hand, Yuchan grabbed onto Byeongkwan’s thigh and gently kneaded the thick muscle there to ground both of them. He pulled back enough to cradle the tip on his tongue, then sat up all the way so a string of saliva kept them connected. It broke when he wiped his lips with his fingers. Yuchan dove back down to leave some kisses and bites along Byeongkwan’s inner thighs. The grip on his hair loosened, but Byeongkwan encouraged his ministrations by scratching lightly at the nape of Yuchan’s neck, causing Yuchan to hum in approval, the vibrations feeling suspiciously like a purring cat.

Yuchan crawled back up into Byeongkwan’s lap to give the same treatment to his neck and then finally his lips, not protesting in the slightest when Byeongkwan’s tongue slid into his mouth.

“Mmm,” Yuchan said as he pulled back, a hazy smile already on his lips, “you wanna move to the bathroom?”

He could feel Byeongkwan’s body temperature spike underneath him.

“Yeah, let’s go.”

Byeongkwan shoved his hands under Yuchan’s thighs and shifted forward, easily standing and lifting Yuchan up at the same time. Yuchan squealed, falling forward until their chests were pressed together, and wrapped his arms tightly around Byeongkwan’s neck. He ducked his head down to rest there too, content to breathe in Byeongkwan’s scent as he carried him across their apartment.

Yuchan crossed his ankles around Byeongkwan’s hips as he carried him with little effort across their apartment. Once they got into the bathroom, Yuchan let his feet touch the floor and Byeongkwan settled to sit on the edge of the bathtub, wasting no time to pull Yuchan towards him by the waist of his pants. He pulled them down over his thighs, the lack of underwear making for a smooth glide as Yuchan’s dick sprung free. Byeongkwan traced his clawed fingers up Yuchan’s thighs to grip lightly at his waist. He pulled him closer still and pushed his hands further up his sides and up his torso to push his shirt up, allowing him to leave kisses on the bare skin of Yuchan’s abdomen.

The thin layer of muscle flexed slightly at the contact, and when Byeongkwan moved his head to lick a stripe up the underside of Yuchan’s cock, he let out a beautiful moan and his knees nearly buckled, catching himself on Byeongkwan’s shoulders.

“This- this is supposed to be about you,” Yuchan said, wiggling the rest of the way out of his shirt, embarrassed for having to catch his breath after a relatively small gesture.

“Mmm,” Byeongkwan agreed. He looked up at Yuchan through his lashes. “Why don’t we get on with it then?”

Yuchan promptly turned around to prepare a toothbrush, wetting it and putting on a fair amount of toothpaste. Satisfied, he turned around to grab the spare container of lube they kept in the bathroom, and held it out to Byeongkwan to open it. Byeongkwan spread a generous amount over his own cock, then held it out so Yuchan could coat his fingers so he could make sure his hole was stretched properly. Yuchan held the toothbrush out of the way with one hand as he moved the other to balance on Byeongkwan’s shoulder. One of Byeongkwan’s hands held his own dick steady, while the other came to rest on Yuchan’s thigh, easily guiding him to line up.

The first breach was always a surprise. No matter how many times Yuchan bottomed, it always coaxed a breathy moan out of him. He sank down slowly as both of Byeongkwan’s hands now held his hips.

“Breathe, baby,” he whispered into Yuchan’s neck, pressing his fingers further into his skin.

Yuchan could feel the sharp point of each of his claws now making contact with his skin; at least two or three of them were bound to draw blood. The thought spurred him on, letting his lower body relax to make it easier. With one long exhale, he took the rest of Byeongkwan’s cock. Byeongkwan groaned at the feeling, and in anticipation for what was coming next.

Before anything else, however, Yuchan leaned down once more to capture Byeongkwan’s lips in a kiss. It was such a gentle brush of lips, Byeongkwan couldn’t help but huff out a little laugh, given that Yuchan was fully seated on his cock.

“Getting sentimental?” He asked against Yuchan’s lips, barely pulling back a millimeter to get the words out.

“No,” Yuchan pouted, meaning he definitely was. “I’m just happy to do this with you, that’s all.”

At least it was a half-truth, Byeongkwan supposed.

“Now,” Yuchan continued, gripping Byeongkwan’s jaw with one hand under his chin, “open wide.”

Byeongkwan did not have to be told twice. He opened his mouth yet again to reveal his teeth, but this time could feel Yuchan clench around his cock in anticipation. He focused all of his self control on keeping his mouth open, rather than closing it to mask his groan like he usually would. Of course, Yuchan noticed.

“Oh, so  _ this _ is how I get you to be loud for me, hmm?” He teased. “This’ll be fun.”

Although he was the real life monster in the room, Byeongkwan couldn’t help but be just a little bit scared of the mischievous twinkle in Yuchan’s eyes as he said the words.

Yuchan once again set to work, carefully brushing Byeongkwan’s teeth starting with the molars. Or, what he assumed were the molars—Byeongkwan had a lot more teeth of different shapes and sizes than a human’s, most of which he wasn’t sure he would be able to name and definitely not with most of his brain power focused on Byeongkwan’s cock sitting heavily within him. Yuchan was careful not to move too much lest he slip and cut himself on the teeth again, but he couldn’t help but squirm when Byeongkwan’s ragged breathing hitched and he let a moan escape.

“Do you need to spit?” Yuchan asked a few moments later. Byeongkwan nodded. “Lean towards the drain then, I’ll wait.”

Byeongkwan leaned over to take care of the spit and toothpaste that had collected in his mouth, and Yuchan took the little break as an opportunity to grind a couple of circles with his hips. After being deprived of anything more than just tight warmth around his cock, Byeongkwan couldn’t help but to buck his hips up into Yuchan.

“Shh, don’t get too excited baby, I’m only halfway done,” Yuchan said, drawing his hand down the side of Byeongkwan’s face.

He breathed deep and leaned into the touch. 

“Keep.. hh-keep going then.” Byeongkwan somehow still managed to keep a demanding tone, which spurred Yuchan on to move his hand back beneath his jaw to hold his face steady.

Byeongkwan’s eyes slipped closed as he soaked in the feeling of Yuchan wrapped tight around his cock along with the soft circles Yuchan was focusing so intently on brushing over his teeth. The intimacy of having his boyfriend’s attention focused solely on his mouth and the gentle pressure against his teeth sent shivers down his spine. Byeongkwan lost himself in the sensations, no longer caring to attempt to hide the sounds, almost mewls, that left his throat from time to time.

He only opened his eyes some time later when Yuchan squeezed slightly on his jaw to get his attention.

“Spit again?” Yuchan asked.

Byeongkwan obliged, then waited as Yuchan leaned over to turn on the spigot and quickly rinse the toothbrush. He placed it on the edge of the tub, then turned back to gently wipe over Byeongkwan’s lips and the corners of his mouth with his thumb.

“Brushing’s done,” he announced, so quietly next to Byeongkwan’s ear.

“Mmm, it appears so,” Byeongkwan agreed. His voice was barely more than a rumble that reverberated between their chests.

Yuchan wasted no time drawing circles with his hips over Byeongkwan’s cock. He almost didn’t notice until that moment how hard his own was where it laid between their bodies until one particularly hard thrust dragged the tip against Byeongkwan’s abs. The sudden stimulation ripped a needy and breathless whine from Yuchan’s throat, and it was all Byeongkwan needed to grab Yuchan’s thighs as tight as he would let himself and begin to fuck up into Yuchan’s body. He fell forward, catching himself with his forearms over Byeongkwan’s shoulders, as Byeongkwan lifted him up and dropped him back down on his cock. The head slammed directly into Yuchan’s prostate, and after a handful of successive thrusts, Yuchan was coming with his eyes screwed shut and a shout of Byeongkwan’s name on his lips.

Byeongkwan wasn’t far behind, only taking a few more seconds after Yuchan to reach his own climax. He carefully pulled Yuchan off of his cock and let him rest perched on his thighs, still slumped against his chest. Byeongkwan carded his fingers through Yuchan’s hair until they both caught their breath. The featherlight touches from the sharp points of Byeongkwan’s claws against his scalp were almost enough to lull Yuchan to sleep right there, if not for the come drying between their stomachs and leaking from Yuchan’s hole.

“Was it good?” Yuchan mumbled once he gained the strength to string together a coherent sentence.

“Mmm, yes, baby.” Byeongkwan pressed a loving and minty kiss just above Yuchan’s ear. “You were perfect for me as always.”

“If you ever need brushing help again... you know who to call,” Yuchan yawned while Byeongkwan chuckled lightly under him. 

He would be sure to take him up on that offer in the future. For now, just a bath and maybe a cuddly nap where in order.

**Author's Note:**

> thank u so so much for reading and supporting me on this uh.. exploration lolol stay tuned for more a.c.e fics in the future!! i had a great time learning to write some new boys and im not stopping any time soon >:)
> 
> come find me on twitter! ddeonghwaa (sfw) and hwaslesbian (nsfw, 18+ only!!!)


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